RE: Would you shoot a mature half racked buck?
For me age matters just as much as rack size. Him being busted makes it no less a trophy in my eyes. 4.5+ year old buck around here are very rare, I am lucky to see one, let alone get a shot at it so he's getting drilled.
As for the mount part, that I don't know, it would minimum be a skull mount, depends on my mood at the time if I would do a full shoulder mount.